The present invention relates to a fiber-reinforced, tubular food casing based on regenerated cellulose. This casing is preferably used as a sausage casing.
Fiber-reinforced cellulose-hydrate-based food casings have been on the market since as early as 1933 in the U.S.A. and since 1936 in Germany and have been successively improved since then. They are generally produced by the viscose process, in which a cellulose xanthogenate solution, termed a "viscose solution", is applied to a usually tubular nonwoven fiber web. If this viscose solution is only applied to the outside, one speaks of an "outer-viscosing" (DE-A 19 65 129), while coating the outside and inside is termed "double-viscosing" (DE-A 19 65 130). The viscose-coated fibrous material is then conducted through spinning and precipitation baths, each of which contain sulfuric acid, ammonium sulfate and sodium sulfate at various concentrations. The viscose is first coagulated, and cellulose hydrate is then regenerated via xanthogenic acid. The cellulose hydrate tube produced in this way is then conducted through a plurality of washing baths. The spinning speed (and correspondingly the speed at which the casing is drawn through the baths) is about 20 to 28 m/min, depending on the sausage skin spinning machine used. The cellulose hydrate casings are conventionally further treated with a secondary softener, such as glycerol, and dried.
The nonwoven fiber web (fiber paper) generally comprises hemp fibers. Fiber papers having a weight of 13 g, 15 g, 17 g, 19 g, 21 g, 23.7 g and 25.4 g per square meter are conventionally used. The contents of the regenerated cellulose and of the softener remain relatively constant. Thus the cellulose hydrate content is generally 40 to 55 g/m.sup.2, and the glycerol content is generally 15 to 30 g/m.sup.2. The food casings additionally contain about 8 to 10% by weight of water, based on their total weight, which--depending on the diameter--is about 75 to 105 g/m.sup.2. They are opaque, so that their contents cannot be discerned, and they are additionally stiff, which hinders fabrication and processing.
One potential method for solving these problems is to use lighter fiber paper. Thus, WO 91/09530 (=EP-B 0 460 410) discloses a tubular cellulose-hydrate-based food casing which is reinforced by a long-fibered manilla fiber paper having a weight of no more than 15 g/m.sup.2 (in the air-dried state).
The use of thinner paper with a constant amount of viscose is relatively cost-intensive. A reduction in the viscose solution with a constant fiber-paper weight to improve the transparency, however, leads to greatly decreased strength.